CVE-2016-7214

Vulnerability

The vulnerability resides in the Windows kernel-mode driver (win32k.sys) and affects a wide range of Windows versions, including Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, and 1607, and Windows Server 2016 [1]. It is triggered when the driver improperly handles objects in memory, leading to an information disclosure condition that can be exploited to bypass Address Space Layout Randomization (ASLR) [1]. No special configuration is required; the code path is reachable by any local user who can execute a crafted application.

Exploitation

An attacker must have local access to the system and the ability to run a specially crafted application [1]. The attacker does not need elevated privileges or user interaction beyond executing the malicious program. The crafted application triggers the memory handling flaw in win32k.sys, causing the kernel to disclose sensitive memory layout information that would otherwise be protected by ASLR [1]. The exact sequence of steps involves invoking specific system calls or API functions that exercise the vulnerable code path.

Impact

Successful exploitation allows the attacker to bypass ASLR, gaining knowledge of the memory layout of the kernel and other processes [1]. This information disclosure is a stepping stone for further attacks, such as exploiting other vulnerabilities that require precise memory addresses. The attacker does not gain code execution or privilege escalation directly from this vulnerability, but the disclosed information significantly reduces the difficulty of exploiting other flaws. The impact is limited to information disclosure, with no direct compromise of confidentiality, integrity, or availability beyond the leaked memory addresses.

Mitigation

Microsoft released security update MS16-135 (KB 3199135) on November 8, 2016, which addresses this vulnerability by correcting how the Windows kernel-mode driver handles objects in memory [1]. All affected Windows versions received the update as part of that bulletin. No workarounds are documented; applying the update is the only mitigation. Users should ensure their systems are fully patched to prevent exploitation.